Transmission and receiving using spreading modulation for spread spectrum communications and thereof apparatus

ABSTRACT

The present invention is related to a method and an apparatus for the orthogonal complex-domain spreading modulation in CDMA spread spectrum communication system when there are channels with statistically higher transmitting power. In CDMA spread spectrum communication systems with a transmitter and a receiver, the transmitter according to the invention has several channels with different information. Two channels with higher power than the others, which are spread in the conventional scheme, are spread with the orthogonal codes using a complex-domain multiplier. The spread signals are added. Then the signals are scrambled using a complex-domain multiplier with secondary scrambling sequences generated by a special scrambling code generator with primary scrambling sequences as inputs. The receiver does reverse operation of the transmitter.

TECHNICAL FIELD

This invention is concerned with spreading modulation methods fororthogonal multiple channel transmitters in CDMA (code division multipleaccess) communication systems. More particularly it is related toorthogonal complex-domain spreading modulation methods for CDMAcommunication systems when there are channels with statistically highertransmitting power.

BACKGROUND ART

In description of the prior art, the same reference number is used for acomponent having the same function as that of the present invention.FIG. 1 shows a schematic diagram for a conventional CDMA transmitterwith orthogonal multiple channels. The transmitter in FIG. 1 is based onthe cdma2000 system, which is one of the candidates for IMT-2000(International Mobile Telecommunications-2000) system as a thirdgeneration mobile communication systems. The transmitter has 5orthogonal channels: A Pilot CHannel (PiCH) used for coherentdemodulation; a Dedicated Control CHannel (DCCH) for transmittingcontrol information; a Fundamental CHannel (FCH) for transmitting lowspeed data such as voice; and two Supplementary CHannels (SCH; SCH1,SCH2) for high-speed data services. Each channel passes through achannel encoder and/or an interleaver (not shown in FIG. 1) according tothe required quality of the channel.

Each channel performs the signal conversion process by changing a binarydata {0, 1} into {+1, −1}. Even though it is explained with the changed{+1, −1}, our method can be equally applied to the informationrepresented by several bits, for example, {00, 01, 11, 10} is changedinto {+3, +1, −1, −3}. The gain for each channel is controlled based onthe required quality and transmitting data rate by using the gaincontrollers G_(P)(110), G_(D)(112), G_(S2)(114), G_(S1)(116), andG_(F)(118). The gain for each channel is determined by a specificreference gain, and the amplifiers (170, 172) control the overall gain.For example, with G_(P)=1, other gain G_(D), G_(S2), G_(S1), or G_(F)can be controlled. Gain controlled signal for each channel is spread atthe spreader (120, 122, 124, 126, 128) with orthogonal Hadamard codeW_(PiCH)[n], W_(DCCH)[n], W_(SCH2)[n], W_(SCH1)[n], or W_(FCH)[n], andis delivered to the adder (130, 132).

Hadamard matrix, H_((p)), comprising the orthogonal Hadamard codes hasthe following four properties:

(1) The orthogonality is guaranteed between the columns and the rows ofan Hadamard matrix. When

$\begin{matrix}{H^{(p)} = {\begin{matrix}{H_{p \times p} = \begin{bmatrix}h_{0,0} & h_{0,1} & \cdots & h_{0,{p - 1}} \\h_{1,0} & h_{1,1} & \cdots & h_{1,{p - 1}} \\\vdots & \vdots & ⋰ & \vdots \\h_{{p - 1},0} & h_{{p - 1},1} & \cdots & h_{{p - 1},{p - 1}}\end{bmatrix}} \\{\begin{bmatrix}\overset{\_}{h_{0}} \\\overset{\_}{h_{1}} \\\vdots \\\overset{\_}{h_{p - 1}}\end{bmatrix} = \left\lbrack {{\overset{\_}{h_{0}}}^{T}\mspace{14mu}{\overset{\_}{h_{1}}}^{T}\cdots\mspace{20mu}{\overset{\_}{h_{p - 1}}}^{T}} \right\rbrack}\end{matrix} =}} & \left\lbrack {{EQUATION}\mspace{14mu} 1} \right\rbrack\end{matrix}$and, ^(h) ^(i,j) ^(∈{+1, −1}; i,j∈{0, 1, 2, . . . , p−1})matrix H^((p)) is a p×p Hadamard matrix if the following equations hold.H _(p×p) H ^(T) _(p×p) =pI ^((p))  [EQUATION 2]h_(i) · h_(j) =p·δ _(i,j)Where I^((p)) is a p×p identity matrix,and ^(δ) ^(i,j) is the Kronecker Delta symbol, which becomes 1 of i=j,and 0 for i≠j.

(2) It is still an Hadamard matrix H^((p)) even if the order of thecolumns and the rows of an Hadamard matrix is changed.

(3) The order of Hadamard matrix H^((p)), p, is 1, 2, or a multiplenumber of 4. In other words, ^(p−{1,2}∪{4n|n∈Z) ⁺ ^(}), where Z⁺ is aset of integers which are greater than 0.

(4) The mn×mn matrix H^((mn)) produced by the Kronecker product (as inEQUATION 3) from a m×m Hadamard matrix A^((m)) and a n×n Hadamard matrixB^((n)) is also an Hadamard matrix.

$\begin{matrix}\begin{matrix}{H_{{mn} \times {mn}} = {A_{m \times m} \otimes B_{n \times n}}} \\{= {\begin{bmatrix}a_{0,0} & a_{0,1} & \cdots & a_{0,{m - 1}} \\a_{1,0} & a_{1,1} & \cdots & a_{1,{m - 1}} \\\vdots & \vdots & ⋰ & \vdots \\a_{{m - 1},0} & a_{{m - 1},1} & \cdots & a_{{m - 1},{m - 1}}\end{bmatrix} \otimes \begin{bmatrix}b_{0,0} & b_{0,1} & \cdots & b_{0,{n - 1}} \\b_{1,0} & b_{1,1} & \cdots & b_{1,{n - 1}} \\\vdots & \vdots & ⋰ & \vdots \\b_{{n - 1},0} & b_{{n - 1},1} & \cdots & b_{{n - 1},{n - 1}}\end{bmatrix}}} \\{= {\begin{bmatrix}{b_{0,0}A} & {b_{0,1}A} & \cdots & {b_{0,{n - 1}}A} \\{b_{1,0}A} & {b_{1,1}A} & \cdots & {b_{1,{n - 1}}A} \\\vdots & \vdots & ⋰ & \vdots \\{b_{{n - 1},0}A} & {b_{{n - 1},1}A} & \cdots & {b_{{n - 1},{n - 1}}A}\end{bmatrix} = \begin{bmatrix}h_{0,0} & h_{0,1} & \cdots & h_{0,{{mn} - 1}} \\h_{1,0} & h_{1,1} & \cdots & h_{1,{{mn} - 1}} \\\vdots & \vdots & ⋰ & \vdots \\h_{{{mn} - 1},0} & h_{{{mn} - 1},1} & \cdots & h_{{{mn} - 1},{{mn} - 1}}\end{bmatrix}}}\end{matrix} & \left\lbrack {{EQUATION}\mspace{14mu} 3} \right\rbrack\end{matrix}$

The present invention describes CDMA systems using the column vectors orrow vectors of a 2^(n)×2^(n) Hadamard matrix ^(H) ^((2″)) as orthogonalcodes, where the 2^(n)×2^(n) Hadamard matrix ^(H) ^((2″)) is generatedfrom a 2×2 Hadamard matrix as shown in EQUATION 4 (n=1, 2, 3, . . . ,8). In particular, the set of the column vectors or the row vectors ofthe produced Hadamard matrix is 2^(n) dimensional Walsh codes.

$\begin{matrix}{\mspace{20mu}{{H^{(2)} = {H_{2 \times 2} = {\begin{bmatrix}{+ 1} & {+ 1} \\{+ 1} & {- 1}\end{bmatrix} = \begin{bmatrix}W_{0}^{(2)} \\W_{1}^{(2)}\end{bmatrix}}}}{H^{(4)} = {H_{4 \times 4} = {{H_{2 \times 2} \otimes H_{2 \times 2}} = {\quad{\begin{bmatrix}{+ 1} & {+ 1} & {+ 1} & {+ 1} \\{+ 1} & {- 1} & {+ 1} & {- 1} \\{+ 1} & {+ 1} & {- 1} & {- 1} \\{+ 1} & {- 1} & {- 1} & {+ 1}\end{bmatrix} = {{\begin{bmatrix}W_{0}^{(4)} \\W_{1}^{(4)} \\W_{2}^{(4)} \\W_{3}^{(4)}\end{bmatrix}H^{(8)}} = {H_{8 \times 8} = {H_{2 \times 2} \otimes {\quad{H_{4 \times 4} = {\quad{\left\lbrack \begin{matrix}{+ 1} & {+ 1} & {+ 1} & {+ 1} & {+ 1} & {+ 1} & {+ 1} & {+ 1} \\{+ 1} & {- 1} & {+ 1} & {- 1} & {+ 1} & {- 1} & {+ 1} & {- 1} \\{+ 1} & {+ 1} & {- 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {- 1} \\{+ 1} & {- 1} & {- 1} & {+ 1} & {+ 1} & {- 1} & {- 1} & {+ 1} \\{+ 1} & {+ 1} & {+ 1} & {+ 1} & {- 1} & {- 1} & {- 1} & {- 1} \\{+ 1} & {- 1} & {+ 1} & {- 1} & {- 1} & {+ 1} & {- 1} & {+ 1} \\{+ 1} & {+ 1} & {- 1} & {- 1} & {- 1} & {- 1} & {+ 1} & {+ 1} \\{+ 1} & {- 1} & {- 1} & {+ 1} & {- 1} & {+ 1} & {+ 1} & {- 1}\end{matrix} \right\rbrack = \left\lbrack \begin{matrix}W_{0}^{(8)} \\W_{1}^{(8)} \\W_{2}^{(8)} \\W_{3}^{(8)} \\W_{4}^{(8)} \\W_{5}^{(8)} \\W_{6}^{(8)} \\W_{7}^{(8)}\end{matrix} \right\rbrack}}}}}}}}}}}}}} & \left\lbrack {{EQUATION}\mspace{14mu} 4} \right\rbrack\end{matrix}$The orthogonal Walsh codes of the above mentioned Hadamard matrixH^((p)) have the following property (p=2^(n)).

$\begin{matrix}\begin{matrix}{{W_{i}^{(p)} \odot W_{j}^{(p)}} \equiv {\left( {w_{i,0}^{(p)},w_{i,1}^{(p)},\ldots\mspace{14mu},w_{i,{p - 1}}^{(p)}} \right) \odot \left( {w_{j,0}^{(p)},w_{j,1}^{(p)},\ldots\mspace{14mu},w_{j,{p - 1}}^{(p)}} \right)}} \\{= \left( {{w_{i,0}^{(p)}w_{j,0}^{(p)}},{w_{i,1}^{(p)}w_{j,1}^{(p)}},\cdots\mspace{14mu},{w_{i,{p - 1}}^{(p)}w_{j,{p - 1}}^{(p)}}} \right)} \\{= \left( {w_{k,0}^{(p)},w_{k,1}^{(p)},\ldots\mspace{14mu},w_{k,{p - 1}}^{(p)}} \right)} \\{= W_{k}^{(p)}}\end{matrix} & \left\lbrack {{EQUATION}\mspace{14mu} 5} \right\rbrack\end{matrix}$Where {i, j, k}⊂{0, 2, 3, . . . , 2^(n)−2}. If i, j, k are representedby binary numbers as in EQUATION 6,i=(i_(n−1), i_(n−2), i_(n−3), . . . , i₁, i₀)₂, j=(j_(n−1), j_(n−2),j_(n−3), . . . , j₁, j₀)₂, k=(k_(n−1), k_(n−2), k_(n−3), . . . , k₁,k₀)₂  [EQUATION 6]the following relation holds among i, j, k:(k_(n−1), k_(n−2), k_(n−3), . . . , k₁, k₀)₂=(i_(n−1)⊕j_(n−1),i_(n−2)⊕j_(n−2), j_(n−3)⊕j_(n−3), . . . , i₁⊕j₁, i₀⊕j₀)_(Z)   [EQUATION7]Here ⊕ represents the eXclusive OR (XOR) operator. Therefore, ^(W) ^(i)^((p)) ^([n]=W) ^(i) ^((p)) ^([n]W) ⁰ ^((p)) ^([n]) for i∈{0, 1, 2, . .. , 2^(n)−1}, and ^(W) ^(2k+1) ^((p)) ^([n]=W) ^(2k) ^((p)) ^([n]W) ¹^((p)) ^([n]) for k∈{0, 1, 2, . . . , 2^(n−1)−1}.

In order to distinguish the orthogonal multiple channels, the Hadamardmatrix H^((p)) is used, and the order of the Hadamard matrix H^((p)),p(=2^(n)) is the Spreading Factor (SF). In direct sequence spreadspectrum communication systems, the spreading bandwidth is fixed, so thetransmission chip rate is also fixed. When there are several channelshaving different data transmission rates with a fixed transmission chiprate, the tree-structured Orthogonal Variable Spreading Factor (OVSF)codes are used (as shown in EQUATION 8) in order to recover the desiredchannels at the receiving terminal using the orthogonal property of thechannels.

The OVSF codes with conversion (“0”

“+1” and “1”

“−1”) and orthogonal Walsh functions are shown in EQUATION 8 andEQUATION 9, respectively. An allocation method of the tree-structuredOVSF codes with the orthogonal property is shown in the followingreferences: (1) F. Adachi, M. Sawahashi and K. Okawa, “Tree-structuredgeneration of orthogonal spreading codes with different lengths forforward link of DS-CDMA mobile radio, “Electronics Letters, Vol. 33,January 1997, pp27–28. (2) U.S. Pat. No. 5,751,761, “System and methodfor orthogonal spread spectrum sequence generation in variable data ratesystems”.

The above equation shows the OVSF codes.

The above equation shows the relation between the OVSF codes andorthogonal Walsh codes.

The outputs (x_(T)[n], y_(T)[n]) of the adder (130, 132) in FIG. 1 canbe written as the following equations:

$\begin{matrix}{{{x_{T}\lbrack n\rbrack} = {{G_{P}{W_{HCH}\lbrack n\rbrack}{D_{HCH}\left\lbrack \left\lfloor \frac{n}{{SF}_{DCH}} \right\rfloor \right\rbrack}} + {G_{D}{W_{DCCH}\lbrack n\rbrack}{D_{DCCH}\left\lbrack \left\lfloor \frac{n}{{SF}_{DCCH}} \right\rfloor \right\rbrack}} + {G_{S2}{W_{SCH2}\lbrack n\rbrack}{D_{SCH2}\left\lbrack \left\lfloor \frac{n}{{SF}_{SCH2}} \right\rfloor \right\rbrack}}}}{{y_{T}\lbrack n\rbrack} = {{G_{F}{W_{FCH}\lbrack n\rbrack}{D_{FCH}\left\lbrack \left\lfloor \frac{n}{{SF}_{FCH}} \right\rfloor \right\rbrack}} + {G_{S1}{W_{SCH1}\lbrack n\rbrack}{D_{SCH1}\left\lbrack \left\lfloor \frac{n}{{SF}_{SCH1}} \right\rfloor \right\rbrack}}}}} & \left\lbrack {{EQUATION}\mspace{14mu} 10} \right\rbrack\end{matrix}$

Here └x┘ is a largest integer not greater than x.

The above mentioned Walsh code W_(PiCH)[n], W_(DCCH)[n], W_(SCH2)[n],W_(SCH1)[n], and W_(FCH)[n] are orthogonal Walsh functions selected fromH^((SF) ^(PiCH) ⁾, H^((SF) ^(DCCH) ⁾, H^((SF) ^(SCH2) ⁾, H^((SF) ^(SCH1)⁾, H^((SF) ^(PCH) ⁾. An allocation method of the orthogonal Walshfunctions to each channel with the orthogonal property follows theallocation method of the OVSF codes. SF_(PiCH), SF_(DCCH), SF_(SCH2),SF_(SCH1), and SF_(FCH) are spreading factors for the correspondingchannels.

For simple explanation, assume the transmitting power of SCH1 and SCH2is assumed to be statistically greater than the power of PiCH, DCCH, andFCH. (This assumption does not change the present invention.) In otherwords, it is assumed the relation G_(S1)>G_(P)+G_(D)+G_(F), andG_(S2)>G_(P)+G_(D)+G_(F), holds statistically. The above assumptionshold in two cases: In the first case, the transmission data rate for thesupplementary channel (SCH1, SCH2) is greater than that of otherchannels (PiCH, DCCH, FCH), and the required quality such as thesignal-to-noise ratio (SNR) for each channel is comparable. In thesecond case, the transmission data rates are comparable, and therequired quality is more restricted. If there are only two channelsavailable in a transmitter, the assumptions hold, and the two channelsare allocated to SCH1 and SCH2. When the assumptions hold, EQUATION 10can be approximated as EQUATION 11.

$\begin{matrix}\begin{matrix}{{x_{T}\lbrack n\rbrack} \simeq {G_{S2}{W_{SCH2}\lbrack n\rbrack}{D_{SCH2}\left\lbrack \left\lfloor \frac{n}{{SF}_{SCH2}} \right\rfloor \right\rbrack}}} \\{{y_{T}\lbrack n\rbrack} \simeq {G_{S1}{W_{SCH1}\lbrack n\rbrack}{D_{SCH1}\left\lbrack \left\lfloor \frac{n}{{SF}_{SCH1}} \right\rfloor \right\rbrack}}}\end{matrix} & \left\lbrack {{EQUATION}\mspace{14mu} 11} \right\rbrack\end{matrix}$

The spreading modulation takes place at the Spreading Modulator (140)with the first inputs (x_(T)[n], y_(T)[n]) and the second inputs, PN(Pseudo-Noise) sequences (C₁[n], C₂[n]), and the outputs (I_(T)[n],Q_(T)[n]) are produced. The peak transmission power to the average powerratio (PAR: Peak-to-Average Ratio) can be improved according to thestructure of the Spreading Modulator (140) and the method how togenerate the scrambling codes (C_(scramble), _(i)[n], C_(scramble),_(Q)[n]) from the inputs of the two PN sequences (C₁[n], C₂[n]).Conventional embodiments for the Spreading Modulator (140) are shown inFIG. 3 a˜3 d. The outputs (I_(T)[n], Q_(T)[n]) of the SpreadingModulator (140) pass through the low-pass-filters (160, 162) and thepower amplifiers (170, 172). Then the amplified outputs are delivered tothe modulators (180, 182) which modulate the signals into the desiredfrequency band using carrier. And the modulator signals are added by theadder (190), and delivered to an antenna.

FIG. 2 shows a schematic diagram for a receiver according to thetransmitter of FIG. 1. The received signals passed through an antennaare demodulated at the demodulators (280, 282) with the same carrierused at the transmitter, and I_(R)[n] and Q_(R)[n] are generated afterpassing through the low-pas filters (260, 262). Then, the spreadingdemodulator (240) generates the signals (x_(R)[n], y_(R)[n]) with two PNsequences (C₁[n], C₂[n]).

In order to pick up the desired channels, i.e., DCCH, FCH, SCH#1, SCH#2,among the received code division multiplexed signals (x_(R)[n],y_(R)[n]), the signals are multiplied by the same orthogonal codeW_(xxCH)[n] (where, xxCH=DCCH or FCH) or W_(yyCH)[n] (where, yyCH=SCH1or SCH2) used at the transmitter, at the de-spreaders (224, 226, 225,227). Now, the signals are integrated during the symbol period (T_(2x)or T_(2y)) proportional to the data rate of the corresponding channel.Since the signals at the receiver are distorted, PiCH is used to correctthe distorted signal phase. Therefore, the signals (x_(R)[n], y_(R)[n])are multiplied by the corresponding orthogonal code W_(PiCH)[n], and areintegrated during the period of T₁ at the integrators (210, 212).

When the PiCH includes additional information such as a control commandto control the transmitting power at the receiver, besides the pilotsignals for the phase correction, the additional information isextracted by the de-multiplexer, and the phase is estimate and correctedusing the part of the pilot signals with the known phase. However, it isassumed that the PiCH does not include any additional information forsimplicity. The phase corrections are performed at the second (kind)complex-domain multipliers (242, 246) using the estimated phaseinformation through the integrators (210, 212). After selecting theoutput port according to the desired channel (DCCH, FCH, SCH1, or SCH2)at the second complex-domain multipliers (242, 246), the receiverrecovers the transmitted data through the de-interleaver and/or thechannel decoder (not shown in FIG. 2).

The first (143) and the second complex-domain multiplier (243 or 246)execute the following function.

[EQUATION 12]

Operations for the first complex-domain multipliers (143, 145):O _(I) [n]+jO _(Q) [n]=(x _(I) [n]+jx _(Q) [n])(y _(I) [n]+jy _(Q) [n])O _(I) [n]=x _(I) [n]y _(I) [n]−x _(Q) [n]y _(Q) [n]O _(Q) [n]=x _(I) [n]y _(Q) ]n]+x _(Q) ]n]y _(I) [n]Operations for the second complex-domain multipliers (242, 243, 245,246):O _(I) [n]+jO _(Q) [n]=(x _(I) [n]+jx _(Q) [n])(y _(I) [n]+jy _(Q) [n])O _(I) [n]=x _(I) [n]y _(I) [n]+x _(Q) [n]y _(Q) [n]O _(Q) [n]=−x _(I) [n]y _(Q) ]n]+x _(Q) ]n]y _(I) [n]

FIG. 7 a and FIG. 7 b show signal constellation diagrams. In FIG. 7 a, asquare represents the input (x_(I)[n]+jx_(Q)[n]) of the firstcomplex-domain multiplier, and a circle shows a normalized output(O_(I)[n]+jO_(Q)[n]) of the first complex-domain multiplier. FIG. 7 bshows four transitions (0, +π/2, −π/2, π) of the first complex-domainmultiplier input (x_(I)[n]+jx_(Q)[n]) according to the time flow. ThePAR characteristic becomes worse at the origin crossing transition (orπ-transition) in FIG. 7 b.

FIG. 3 a shows the schematic diagram for a conventional spreadingmodulator. This spreading modulation method is used in the forward link(from a base station to its mobile station) for a CDMA system of IS-95method. This spreading modulation is called the QPSK (Quadrature PhaseShift Keying) spreading modulation.I _(T) [n]=x _(T) [n]C _(scramble,I) [n]  [EQUATION 13]Q _(T) [n]=y _(T) [n]C _(scramble,Q) [n]

The outputs (C_(scramble, I)[n], C_(scramble, Q)[n]) of the secondaryscrambling code generator shown in FIG. 4 a are given by EQUATION 14. Inother words, the secondary scrambling codes are the same as the primaryscrambling codes.C_(scramble, I) [n]=C ₁ [n]  [EQUATION 14]C_(scramble, Q) [n]=C ₂ [n]In the IS-95 system, x_(T)[n]=y_(T)[n], but generally x_(T)[n]≠y_(T)[n]in the QPSK spreading modulation. For |I_(T)[n]|=|Q_(T)[n]|=1 based onthe normalization, the possible transitions of the signal constellationpoint occurring in the QPSK spreading modulation are shown in EQUATION15. The probability for {0, +π/2, −π/2, π) transition is equally 1/4 foreach transition.

${\arg\left( \frac{{I_{T}\left\lbrack {n + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n + 1} \right\rbrack}}{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}} \right)} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}},\pi} \right\}$

FIG. 8 a shows the transitions of the signal constellation point for theQPSK spreading modulation when I_(T)[n]=±1, Q_(T)[n]=±1, and SF=4. Forn≡0 mod SF, (I_(T)[n], Q_(T)[n]) becomes one of (+1, +1), (+1, −1), (−1,−1), (−1, +1) with an equal probability of 1/4. The transition isassumed to start at (+1, +1). There is no change in the signalconstellation diagram at a chip time of n+1/2. At a chip time of n+1,(I_(T)[n], Q_(T)[n]) transits to one of (+1, +1), (+1, −1), (−1, −1),(−1, +1) with an equal probability of 1/4. FIG. 8 a shows the case of(+1, −1) transition.

There is no change in the signal constellation diagram at a chip time ofn+3/2. At a chip time of n+2, (I_(T)[n], Q_(T)[n]) transits to one of(+1, +1), (+1, −1), (−1, −1), (−1, +1) with an equal probability of 1/4.FIG. 8 a shows the case of (−1, +1) transition. The PAR characteristicbecomes worse in this case due to an origin crossing transition(π-transition).

There is no change in the signal constellation diagram at a chip time ofn+5/2. At a chip time of n+3, (I_(T)[n], Q_(T)[n]) transits to one of(+1, +1), (+1, −1), (−1, −1), (−1, +1) with an equal probability of 1/4.FIG. 8 a shows the case of (−1, −1) transition.

There is no change in the signal constellation diagram at a chip time ofn+7/2. At a chip time of n+4, (I_(T)[n], Q_(T)[n]) transits to one of(+1, +1), (+1, −1), (−1, −1), (−1, +1) with an equal probability of 1/4.The above transition process is repeated according to the probability.

FIG. 3 b shows a schematic diagram for another conventional spreadingmodulator. This spreading modulation method is used in the reverse link(from a mobile station to its base station) for the IS-95 CDMA system.This spreading modulation is called the OQPSK (Offset QPSK) spreadingmodulation, and the output signals are governed by EQUATION 16.

$\begin{matrix}\begin{matrix}{{I_{T}\lbrack n\rbrack} = {{x_{T}\lbrack n\rbrack}{C_{{scramble}.I}\lbrack n\rbrack}}} \\{{Q_{T}\lbrack n\rbrack} = {{y_{T}\left\lbrack {n - \frac{1}{2}} \right\rbrack}{C_{{scramble}.Q}\left\lbrack {n - \frac{1}{2}} \right\rbrack}}}\end{matrix} & \left\lbrack {{EQUATION}\mspace{14mu} 16} \right\rbrack\end{matrix}$

The outputs (C_(scramble, I)[n], C_(scramble, Q)[n]) of the secondaryscrambling code generator in FIG. 4 a are given by EQUATION 17. In otherwords, the secondary scrambling codes are the same as the primaryscrambling codes, as in the previous QPSK spreading modulation.C_(scramble, I)[n]=C₁[n]  [EQUATION 17]C_(scramble, Q)[n]=C₂[n]Generally x_(T)[n]≠y_(T)[n] in OQPSK spreading modulation. For|I_(T)[n]|=|Q_(T)[n]|=1 based on the normalization, the possibletransitions of the signal constellation point occurring in the QPSKspreading modulation are shown in EQUATION 18. The probabilities for {0,+π/2, −π/2, π} transitions are 1/2, 1/4, 1/4, 0, respectively.

$\begin{matrix}\begin{matrix}{{\arg\left( \frac{{I_{T}\left\lbrack {n + {1/2}} \right\rbrack} + {{jQ}_{T}\left\lbrack {n + {1/2}} \right\rbrack}}{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}} \right)} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}}} \right\}} \\{{\arg\left( \frac{{I_{T}\left\lbrack {n + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n + 1} \right\rbrack}}{{I_{T}\left\lbrack {n + {1/2}} \right\rbrack} + {{jQ}_{T}\left\lbrack {n + {1/2}} \right\rbrack}} \right)} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}}} \right\}}\end{matrix} & \left\lbrack {{EQUATION}\mspace{14mu} 18} \right\rbrack\end{matrix}$

In OQPSK spreading modulation shown in FIG. 3 b, the signal of theorthogonal phase channel (Q-channel) is delayed by a half cup (Tc/2)relative to the signal of the in-phase channel (I-channel) in order toimprove the PAR characteristic of QPSK spreading modulation in FIG. 3 a.Due to a half chip (Tc/2) delay, the codes of the I-channel andQ-channel signals cannot be changed simultaneously. Thus, theπ-transition crossing the origin is prohibited, and the PARcharacteristic is improved.

FIG. 8 b shows the transitions of the signal constellation point for theOQPSK spreading modulation when I_(T)[n]=±1, Q_(T)[n]=±1, and SF=4. Forn≡0 mod SF, (I_(t)[n], Q_(T)[n]) becomes one of (+1, +1), (+1, −1), (−1,−1), (−1, +1) with an equal probability of 1/4. The transition isassumed to start at (+1, +1). At a chip time of n+1/2, (I_(T)[n],Q_(T)[n]) transits to either (+1, +1) or (+1, −1) with an equalprobability of 1/2. FIG. 8 b shows the case of (+1, +1) transition: At achip time of n+1, (I_(T)[n], Q_(T)[n]) transits to either (+1, +1) or(−1, +1) with an equal probability of 1/2. FIG. 8 b shows the case of(+1, +1) transition: At a chip time of n+3/2, (I_(T)[n], Q_(T)[n])transits to either (+1, +1) or (+1, −1) with an equal probability of1/2. FIG. 8 b shows the case of (+1, −1) transition: At a chip time ofn+2, (I_(T)[n], Q_(T)[n]) transits to either (+1, −1) or (−1, −1) withan equal probability of 1/2. FIG. 8 b shows the case of (−1, −1)transition: At a chip time of n+5/2, (I_(T)[n], Q_(T)[n]) transits toeither (−1, −1) or (−1, +1) with an equal probability of 1/2. FIG. 8 bshows the case of (−1, +1) transition: At a chip time of n+3, (I_(T)[n],Q_(T)[n]) transits to either (+1, +1) or (−1, +1) with an equalprobability of 1/2. FIG. 8 b shows the case of (−1, +1) transition: At achip time of n+7/2, (I_(T)[n], Q_(T)[n]) transits to either (−1, +1) or(−1, −1) with an equal probability of 1/2. FIG. 8 b shows the case of(−1, −1) transition: At a chip time of n+4, (I_(T)[n], Q_(T)[n])transits to either (+1, −1) or (−1, −1) with an equal probability of1/2. The above transition process is repeated according to theprobability.

FIG. 3 c shows a schematic diagram for another conventional spreadingmodulator. This spreading modulation method is subdivided into threemethods according to the scrambling code generator (150). The firstmethod is used in the forward link (from a base station to its mobilestation) for a W-CDMA (Wideband CDMA) system as another candidate forcdma2000 or IMT-2000 system. This spreading modulation is called theCQPSK (Complex QPSK) spreading modulation, and the output signals aregoverned by EQUATION 19.

$\begin{matrix}{{{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}} = {\left( {{x_{T}\lbrack n\rbrack} + {{jy}_{T}\lbrack n\rbrack}} \right)\left\{ {\frac{1}{\sqrt{2}}\left( {{C_{{scramble},I}\lbrack n\rbrack} + {{jC}_{{scramble},Q}\lbrack n\rbrack}} \right)} \right\}}}{{I_{T}\lbrack n\rbrack} = {{\frac{1}{\sqrt{2}}{x_{T}\lbrack n\rbrack}{C_{{scramble},I}\lbrack n\rbrack}} - {\frac{1}{\sqrt{2}}{y_{T}\lbrack n\rbrack}{C_{{scramble},Q}\lbrack n\rbrack}}}}{{Q_{T}\lbrack n\rbrack} = {{\frac{1}{\sqrt{2}}{x_{T}\lbrack n\rbrack}{C_{{scramble},Q}\lbrack n\rbrack}} - {\frac{1}{\sqrt{2}}{y_{T}\lbrack n\rbrack}{C_{{scramble},I}\lbrack n\rbrack}}}}} & \left\lbrack {{EQUATION}\mspace{14mu} 19} \right\rbrack\end{matrix}$The outputs (C_(scramble, I)[n], C_(scramble, Q)[n]) of the secondaryscrambling code generator in FIG. 4 a are given by EQUATION 20. In otherwords, the secondary scrambling codes are the same as the primaryscrambling codes, as described in the previous QPSK and OQPSK spreadingmodulation.C_(scramble, I)[n]=C₁[n]  [EQUATION 20]C_(scramble, Q)[n]=C₂[n]Generally x_(T)[n]≠y_(T)[n] in CQPSK spreading modulation. For|I_(T)[n]|=|Q_(T)[n]|=1 based on the normalization, the possibletransitions of the signal constellation point occurring in the CQPSKspreading modulation are shown in EQUATION 21. The probability for {0,+π/2, −π/2, π) transition is equally 1/4 for each transition.

$\begin{matrix}{{\arg\left( \frac{{I_{T}\left\lbrack {n + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n + 1} \right\rbrack}}{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}} \right)} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}},\pi} \right\}} & \left\lbrack {{EQUATION}\mspace{14mu} 21} \right\rbrack\end{matrix}$

The previous OQPSK method is effective when the I-channel and Q-channelpowers are the same as in IS-95 reverse link channels. But the Q-channelsignal should be delayed by a half chip, and the amplitude of thetransmitting power for I-channel is different from that for Q-channel inthe case of FIG. 1 when several channels with different transmittingpowers are using orthogonal channels. The linear range of the amplifiershould be selected based upon the largest transmitting signal power inorder to reduce the neighboring channel interference from the signaldistortion and the inter-modulation.

On the other hand, in CQPSK spreading modulation, I-channel signal(x_(T)[n]) and Q-channel signal (y_(T)[n]) are multiplied incomplex-domain by the secondary scrambling codes, C_(scramble, I)[n] andC_(scramble, Q)[n] of the same amplitude. Therefore, the smaller ofsignal power level of the two (I and Q) become large, and the larger ofsignal power level of the two becomes small; the two signal power levelsare equalized statistically. The CQPSK spreading modulation is moreeffective to improve the PAR characteristic when there are multiplechannels with different power levels. In the CQPSK spreading modulation,x_(T)[n]+jy_(T)[n] makes an origin crossing transition (π-transition)with a probability of 1/4.

FIG. 8 c shows the transitions of the signal constellation point for theCQPSK spreading modulation when x_(T)[n]=±1, y_(T)[n]=±1, I_(T)[n]=±1,Q_(T)[n]=±1, and SF=4. For n≡0 mod SF, x_(T)[n]+jy_(T)[n] andC_(scramble, I)[n]+jC_(scramble, Q)[n] become one of 1+j, 1−j, −1−j,−1+j with an equal probability of 1/4, and it is assumed thatx_(T)[n]+jy_(T)[n]=1+j and C_(scramble, I)[n]+jC_(scramble, Q)[n]=1+j;in other words, in this case, I_(T)[n]+jQ_(T)[n]=0+j√{square root over(2)}. And this equation becomes I_(T)[n]+jQ_(T)[n]=0+jl due to thenormalization. There is no change in the signal constellation diagram ata chip time of n+1/2. At a chip time of n+1, x_(T)[n]+jy_(T)[n] transitsto one of 1+j, 1−j, −1−j, and −1+j, andC_(scramble, I)[n]+jC_(scramble, Q)[n] also transits to one of 1+j, 1−j,−1−j, and −1+j.

The second method is used in the reverse link (from a mobile station toits base station) for a G-CDMA (Global-CDMA) I and II systems as anothercandidate for IMT-2000 system proposed at InternationalTelecommunications Union (ITU, http://www.itu.int) in June 1998. Thisspreading modulation is called the OCQPSK (Orthogonal Complex QPSK)spreading modulation referring to Korean Patent NO. 10-269593-0000. Thefollowing relations hold when only an even number is assigned to thesubscript of the orthogonal Walsh code for each channel.

$\begin{matrix}{{{x_{T}\left\lbrack {2n} \right\rbrack} \simeq {x_{T}\left\lbrack {{2n} + 1} \right\rbrack}}{{y_{T}\left\lbrack {2n} \right\rbrack} \simeq {y_{T}\left\lbrack {{2n} + 1} \right\rbrack}}{{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}} = {\left( {{x_{T}\lbrack n\rbrack} + {{jy}_{T}\lbrack n\rbrack}} \right)\left\{ {\frac{1}{\sqrt{2}}\left( {{C_{{scramble},I}\lbrack n\rbrack} + {{jC}_{{scramble},Q}\lbrack n\rbrack}} \right)} \right\}}}{{I_{T}\lbrack n\rbrack} = {{\frac{1}{\sqrt{2}}{x_{T}\lbrack n\rbrack}{C_{{scramble},I}\lbrack n\rbrack}} - {\frac{1}{\sqrt{2}}{y_{T}\lbrack n\rbrack}{C_{{scramble}.Q}\lbrack n\rbrack}}}}{{Q_{T}\lbrack n\rbrack} = {{\frac{1}{\sqrt{2}}{x_{T}\lbrack n\rbrack}{C_{{scramble},Q}\lbrack n\rbrack}} + {\frac{1}{\sqrt{2}}{y_{T}\lbrack n\rbrack}{C_{{scramble}.I}\lbrack n\rbrack}}}}} & \left\lbrack {{EQUATION}\mspace{14mu} 22} \right\rbrack\end{matrix}$

The outputs (C_(scramble, I)[n], C_(scramble, Q)[n]) of the secondaryscrambling code generator in FIG. 4 b are given by EQUATION 23. Since W₀^((p))[n]=1, the secondary scrambling code generators in FIG. 4 b andFIG. 4 c are the same for k=0.C _(scramble,I) [n]+jC _(scramble,Q) [n]=C ₁ [n](W _(2k) ^((p)) [n]+jW_(2k+1) ^((p)) [n])   [EQUATION 23]C _(scramble,I) [n]=C ₁ [n]W _(2k) ^((p)) [n]C _(scramble,Q) [n]=C ₁ [n]W _(2k+1) ^((p)) [n]Where p is a power of 2 (i.e., p=2^(n)), and

$k \in \left\{ {0,1,2,\cdots\mspace{14mu},{\frac{p}{2} - 1}} \right\}$

Generally x_(T)[n]≠y_(T)[n] in OCQPSK spreading modulation. For|I_(T)[n]|=|Q_(T)[n]|=1 based on the normalization, the possibletransitions of the signal constellation point occurring in the OCQPSKspreading modulation are shown in EQUATION 24. The probabilities for {0,+π/2, −π/2, π} transitions are 0, 1/2, 1/2, and 0 for n=2t+1 (oddnumber), and 1/4, 1/4, 1/4, and 1/4 in case of n=2t (even number) foreach transition, respectively.

$\begin{matrix}{{\frac{{I_{T}\left\lbrack {n + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n + 1} \right\}}}{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}} = {\frac{\left( {{x_{T}\left\lbrack {n + 1} \right\rbrack} + {{jy}_{T}\left\lbrack {n + 1} \right\rbrack}} \right)\left( {{C_{{scramble},I}\left\lbrack {n + 1} \right\rbrack} + {{jC}_{{scramble},Q}\left\lbrack {n + 1} \right\rbrack}} \right)}{\left( {{x_{T}\lbrack n\rbrack} + {{jy}_{T}\lbrack n\rbrack}} \right)\left( {{C_{{scramble},I}\lbrack n\rbrack} + {{jC}_{{scramble},Q}\lbrack n\rbrack}} \right)}\mspace{250mu} = {\frac{{x_{T}\left\lbrack {n + 1} \right\rbrack} + {{jy}_{T}\left\lbrack {n + 1} \right\rbrack}}{{x_{T}\lbrack n\rbrack} + {{jy}_{T}\lbrack n\rbrack}} \cdot \frac{{C_{1}\left\lbrack {n + 1} \right\rbrack}\left( {{W_{2k}^{(p)}\left\lbrack {n + 1} \right\rbrack} + {{jW}_{{2k} + 1}^{(p)}\left\lbrack {n + 1} \right\rbrack}} \right)}{{C_{1}\lbrack n\rbrack}\left( {{W_{2k}^{(p)}\lbrack n\rbrack} + {{jW}_{{2k} + 1}^{(p)}\lbrack n\rbrack}} \right)}}}}\text{}{{\arg\left\{ \frac{{I_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 1} \right\rbrack}}{{I_{T}\left\lbrack {2t} \right\rbrack} + {{jQ}_{T}\left\lbrack {2t} \right\rbrack}} \right\}} \in \left\{ {{+ \frac{\pi}{2}},{- \frac{\pi}{2}}} \right\}}{{\arg\left\{ \frac{{I_{T}\left\lbrack {{2t} + 2} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 2} \right\rbrack}}{{I_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 1} \right\rbrack}} \right\}} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}},\pi} \right\}}} & \left\lbrack {{EQUATION}\mspace{14mu} 24} \right\rbrack\end{matrix}$In the OCQPSK spreading modulation, the following properties are used:For W_(2k) ^((p))[n],

${k \in \left\{ {0,1,2,\ldots\mspace{14mu},{\frac{P}{2} - 1}} \right\}};$W_(2k) ^((p))[2t]=W_(2k) ^((p))[2t+1], t∈{0, 1, 2, . . . }.And for W_(2k+1) ^((p))[n],

${k \in \left\{ {0,1,2,\ldots\mspace{14mu},{\frac{P}{2} - 1}} \right\}};$W_(2k+1) ^((p))[2t]=−W_(2k+1) ^((p))[2t+1], t∈{0, 1, 2, . . . }.

The orthogonal Walsh codes with even number subscripts are used for thechannel identification except for the case when the orthogonal Walshcodes with odd number subscripts must be used for the channelidentification due to the high transmitting data rate. Becausex_(T)[2t]=x_(T)[2t+1], y_(T)[2t]=y_(T)[2t+1], t∈{0, 1, 2, . . . }, thefollowing approximation holds as described in EQUATION 25.

$\begin{matrix}{{{x_{T}\lbrack n\rbrack} + {{jy}_{T}\lbrack n\rbrack}} \simeq {{G_{S2}{W_{SCH2}\lbrack n\rbrack}{D_{SCH2}\left\lbrack \left\lfloor \frac{n}{{SF}_{SCH2}} \right\rfloor \right\rbrack}} + {{jG}_{S1}{W_{SCH1}\lbrack n\rbrack}{D_{SCH1}\left\lbrack \left\lfloor \frac{n}{{SF}_{SCH1}} \right\rfloor \right\rbrack}}}} & \left\lbrack {{EQUATION}\mspace{14mu} 25} \right\rbrack\end{matrix}$

In the OCQPSK spreading modulation, avoiding the origin crossingtransition (π-transition) which makes worse the PAR characteristic forn=2t+1, the PAR characteristic of the spreading signals is improvedcompared to the CQPSK spreading modulation. At n=2t, x_(T)[n]+jy_(T)[n]makes an origin crossing transition (π-transition) with a probability of1/4 as in the CQPSK spreading modulation, while, at n=2t+1, thecorresponding probability is zero. Therefore, the average probabilityfor the origin crossing transition (π-transition) decreases to 1/8 from1/4. C₁[n] for the scrambling in FIG. 4 b is also used in identifyingthe transmitter.

The third method is used in the reverse link (from a mobile station toits base station) for a W-CDMA system as another candidate for cdma2000and IMT-2000 system. This spreading modulation is POCQPSK (PermutedOrthogonal Complex QPSK) spreading modulation referring to Korean PatentNO. 10-269593-0000. The following relations hold when only an evennumber is assigned to the subscript of the orthogonal Walsh code foreach channel.

$\begin{matrix}{{{x_{T}\left\lbrack {2\; n} \right\rbrack} \simeq {x_{T}\left\lbrack {{2\; n} + 1} \right\rbrack}}{{y_{T}\left\lbrack {2\; n} \right\rbrack} \simeq {y_{T}\left\lbrack {{2\; n} + 1} \right\rbrack}}\begin{matrix}{{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}} = {\left( {{x_{T}\lbrack n\rbrack} + {{jy}_{T}\lbrack n\rbrack}} \right)\left\{ {\frac{1}{\sqrt{2}}\left( {{C_{{scramble},I}\lbrack n\rbrack} + {{jC}_{{scramble},Q}\lbrack n\rbrack}} \right)} \right\}}} \\{{I_{T}\lbrack n\rbrack} = {{\frac{1}{\sqrt{2}}{x_{T}\lbrack n\rbrack}{C_{{scramble},I}\lbrack n\rbrack}} - {\frac{1}{\sqrt{2}}{y_{T}\lbrack n\rbrack}{C_{{scramble},Q}\lbrack n\rbrack}}}} \\{{Q_{T}\lbrack n\rbrack} = {{\frac{1}{\sqrt{2}}{x_{T}\lbrack n\rbrack}{C_{{scramble},Q}\lbrack n\rbrack}} + {\frac{1}{\sqrt{2}}{y_{T}\lbrack n\rbrack}{C_{{scramble},I}\lbrack n\rbrack}}}}\end{matrix}} & \left\lbrack {{EQUATION}\mspace{14mu} 26} \right\rbrack\end{matrix}$The outputs (C_(scramble, I)[n], C_(scramble, Q)[n]) of the secondaryscrambling code generator in FIG. 4 d are given by EQUATION 27.C _(scramble,I) [n]+jC _(scramble,Q) [n]=C ₁ [n](W _(2k) ^((p)) [n]+jC′₂ [n]W _(2k+1) ^((p)) [n])   [EQUATION 27]C _(scramble,I) [n]=C ₁ [n]W _(2k) ^((p)) [n]C _(scramble,Q) [n]=C ₁ [n]C′ ₂ [n]W _(2k+1) ^((p)) [n]C′ ₂[2t]=C′ ₂[2t+1]=C ₂[2t], t∈{0, 1, 2, . . . }

Generally x_(T)[n]≠y_(T)[n] in POCQPSK spreading modulation. For|I_(T)[n]|=|Q_(T)[n]|=1 based on the normalization, the possibletransitions of the signal constellation point occurring in the POCQPSKspreading modulation are shown in EQUATION 28. The probabilities for {0,+π/2, −π/2, π} transition is 0, 1/2, 1/2, and 0 for n=2t+1 (odd number),and 1/4, 1/4, 1/4, and 1/4 in case of n=2t (even number) for eachtransition, respectively.

${\frac{{I_{T}\left\lbrack {{2t} + 2} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 2} \right\rbrack}}{{I_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 1} \right\rbrack}} = {\frac{\left( {{x_{T}\left\lbrack {{2t} + 2} \right\rbrack} + {{jy}_{T}\left\lbrack {{2t} + 2} \right\rbrack}} \right)\left( {{C_{{scramble},I}\left\lbrack {{2t} + 2} \right\rbrack} + {{jC}_{{scramble},Q}\left\lbrack {{2t} + 2} \right\rbrack}} \right)}{\left( {{x_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jy}_{T}\left\lbrack {{2t} + 1} \right\rbrack}} \right)\left( {{C_{{scramble},I}\left\lbrack {{2t} + 1} \right\rbrack} + {{jC}_{{scramble},Q}\left\lbrack {{2t} + 1} \right\rbrack}} \right)} = {\frac{{x_{T}\left\lbrack {{2t} + 2} \right\rbrack} + {{jy}_{T}\left\lbrack {{2t} + 2} \right\rbrack}}{{x_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jy}_{T}\left\lbrack {{2t} + 1} \right\rbrack}} \cdot \frac{W_{2k}^{(p)}\left\lbrack {{2t} + 2} \right\rbrack}{W_{2k}^{(p)}\left\lbrack {{2t} + 1} \right\rbrack} \cdot \frac{C_{1}\left\lbrack {{2t} + 2} \right\rbrack}{C_{1}\left\lbrack {{2t} + 1} \right\rbrack} \cdot \frac{1 + {{{{jC}^{\prime}}_{2}\left\lbrack {{2t} + 2} \right\rbrack}{W_{1}^{(p)}\left\lbrack {{2t} + 2} \right\rbrack}}}{1 + {{{{jC}^{\prime}}_{2}\left\lbrack {{2t} + 1} \right\rbrack}{W_{1}^{(p)}\left\lbrack {{2t} + 1} \right\rbrack}}}}}}$$\mspace{239mu}{{\arg\left\{ \frac{{I_{T}\left\lbrack {{2t} + 2} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 2} \right\rbrack}}{{I_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 1} \right\rbrack}} \right\}} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}},\pi} \right\}}$$\begin{matrix}{\frac{{I_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 1} \right\rbrack}}{{I_{T}\left\lbrack {2t} \right\rbrack} + {{jQ}_{T}\left\lbrack {2t} \right\rbrack}} = {\frac{{x_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jy}_{T}\left\lbrack {{2t} + 1} \right\rbrack}}{{x_{T}\left\lbrack {2t} \right\rbrack} + {{jy}_{T}\left\lbrack {2t} \right\rbrack}} \cdot \frac{{C_{{scramble},I}\left\lbrack {{2t} + 1} \right\rbrack} + {{jC}_{{scramble},Q}\left\lbrack {{2t} + 1} \right\rbrack}}{{C_{{scramble},I}\left\lbrack {2t} \right\rbrack} + {{jC}_{{scramble},Q}\left\lbrack {2t} \right\rbrack}}}} \\{= {\frac{C_{1}\left\lbrack {{2t} + 1} \right\rbrack}{C_{1}\left\lbrack {2t} \right\rbrack} \cdot \frac{{W_{2k}^{(p)}\left\lbrack {{2t} + 1} \right\rbrack} + {{{{jC}^{\prime}}_{2}\left\lbrack {{2t} + 1} \right\rbrack}{W_{{2k} + 1}^{(p)}\left\lbrack {{2t} + 1} \right\rbrack}}}{{W_{2k}^{(p)}\left\lbrack {2t} \right\rbrack} + {{{{jC}^{\prime}}_{2}\left\lbrack {2t} \right\rbrack}{W_{{2k} + 1}^{(p)}\left\lbrack {2t} \right\rbrack}}}}} \\{{= {\frac{C_{1}\left\lbrack {{2t} + 1} \right\rbrack}{C_{1}\left\lbrack {2t} \right\rbrack} \cdot \frac{1 - {{{{jC}^{\prime}}_{2}\left\lbrack {2t} \right\rbrack}{W_{1}^{(p)}\left\lbrack {2t} \right\rbrack}}}{1 + {{{{jC}^{\prime}}_{2}\left\lbrack {2t} \right\rbrack}{W_{1}^{(p)}\left\lbrack {2t} \right\rbrack}}}}}{{\arg\left\{ \frac{{I_{T}\left\lbrack {{2t} + 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {{2t} + 1} \right\rbrack}}{{I_{T}\left\lbrack {2t} \right\rbrack} + {{jQ}_{T}\left\lbrack {2t} \right\rbrack}} \right\}} \in \left\{ {{+ \frac{\pi}{2}},{- \frac{\pi}{2}}} \right\}}}\end{matrix}$

The POCQPSK spreading modulation is basically the same as the OCQPSKspreading modulation. Therefore, at n=2t, x_(T)[n]+jy_(T)[n] makes anorigin crossing transition (π-transition) with a probability of 1/4 asdescribed in the CQPSK spreading modulation, while, at n=2t+1, thecorresponding probability is zero. C′₂[n] decimated from C₂[n] is usedin order to compensate for the lack of the randomness due to a periodicrepetition of the orthogonal Walsh functions. The decimation should bemade with the following properties: For t∈{0, 1, 2, . . . } and

${k \in \left\{ {0,1,2,\ldots\mspace{14mu},{\frac{P}{2} - 1}} \right\}},$W_(2k+1) ^((p))[2t]=−W_(2k+1) ^((p))[2t+1], and C′₂[2t]W_(2k+1)^((p))[2t]=−C′₂[2t+1]W_(2k+1) ^((p))[2t+1].Even though C₂[n] is decimated to 2:1 in the above case, 2^(d):1decimation for d∈{1, 2, 3, . . . } is also possible. When2^(d)=max{SF_(PiCH), SF_(DCCH), SF_(SCH2), SF_(SCH1), SF_(FCD)}, therandomness of the POCQPSK is the same as that of the OCQPSK, and therandomness becomes high for 2:1 decimation with d=1. C₁[n] and C₂[n] forthe scrambling to obtain the better spectrum characteristic are alsoused to identify the transmitter through the auto-correlation and thecross-correlation. The number of identifiable transmitters increaseswhen both of C₂[n] and C₂[n] are used as the scrambling codes.

FIG. 9 and FIG. 10 show schematic diagrams for a transmitter and areceiver using the POCQPSK spreading modulation. FIG. 9 shows aschematic diagram for the transmitter based on the cdma2000 system,which is one of the candidates for IMT-2000 system as a third generationmobile communication system. The transmitter has five orthogonalchannels: PiCH, DCCH, FCH, SCH1, and SCH2. Each channel performs thesignal conversion process by changing a binary data {0, 1} into {+1,−1}.

The gain controlled signal for each channel is spread at the spreader(120, 122, 124, 126, 128) with the orthogonal OVSF code W_(PiCH)[n],W_(DCCH)[n], W_(SCH2)[n], W_(SCH1)[n], or W_(FCH)[n], and is deliveredto the adder (130, 132). The spreading modulation takes place at theSpreading Modulator (140) with the first inputs (x_(T)[n], y_(T)[n]) andthe second inputs (the primary scrambling codes; C₁[n] and C₂[n]), andthe outputs (I_(T)[n], Q_(T)[n]) are generated. The spreading modulator(140) comprises the scrambling code generator (510) and the firstcomplex-domain multiplier (143). The scrambling code generator (510)produces the secondary scrambling codes (C_(scramble, I)[n],C_(scramble, Q)[n]) with the primary scrambling codes (C₁[n], C₂[n]) asthe inputs to improve the PAR characteristic. The first complex-domainmultiplier (143) takes x_(T)[n] and y_(T)[n] as inputs and the secondaryscrambling codes (C_(scramble, I)[n], C_(scramble, Q)[n]) as anotherinputs.

The primary scrambling codes (C₁[n], C₂[n]) in the cdma2000 system isproduced by the primary scrambling code generator (550) using three PNsequences (PN_(I)[n], PN_(Q)[n], PN_(long)[n]) as shown in FIG. 5 a withthe following equation:C ₁ [n]=PN _(I) [n]PN _(long) [n]  [EQUATION 29]C ₂ [n]=PN _(Q) [n]PN _(long) [n−1]The secondary scrambling codes (C_(scramble, I)[n], C_(scramble, Q)[n])are given by the following equation:C _(scramble,I) [n]=C ₁ [n]W ₀ ^((p)) [n]=C ₁ [n]  [EQUATION 30]C _(scramble,Q) [n]=C ₁ [n]C′ ₂ [n]W ₁ ^((p)) [n]C′ ₂[2t]=C′ ₂[2t+1]=C ₂[2t], t∈{0, 1, 2, . . .}The outputs (I_(T)[n], Q_(T)[n]) of the Spreading Modulator (140) passthrough the low-pass filters (160, 162) and power amplifiers (170, 172).Then the amplified outputs are delivered to the modulators (180, 182)which modulate the signals into the desired frequency band using acarrier. And the modulated signals are added by the adder (190), anddelivered to an antenna.

FIG. 10 shows a schematic diagram for a receiver according to thetransmission of FIG. 9. The received signals through an antenna aredemodulated at the demodulators (280, 282) with the same carrier used atthe transmitter, and I_(R)[n] and Q_(R)[n] are generated after thesignals pass through the low-pass filters (260, 262). Then, thespreading demodulator (240) produces the signals (x_(R)[n], y_(R)[n])with the primary scrambling codes (C₁[n], C₂[n]). The spreadingdemodulator (240) comprises the scrambling code generator (510) and thesecond complex-domain multiplier (243). The scrambling code generator(510) produces the secondary scrambling codes (C_(scramble, I[n], C)_(scramble, Q)[n]) with the primary scrambling codes (C₁[n], C₂[n]) asthe inputs to improve the PAR characteristic. The second complex-domainmultiplier (243) in the spreading demodulator (240) takes the I_(R)[n],Q_(R)[n] as the first inputs and the secondary scrambling codes(C_(scramble, I)[n], C_(scramble, Q)[n]) as the second inputs. The firstand secondary scrambling codes are generated by the same method as inthe transmitter.

In order to select the desired channels among the outputs (x_(R)[n],y_(R)[n]) of the spreading demodulator (240), the signals are multipliedby the same orthogonal code W_(xxCH)[n] (where, xxCH=DCCH or FCH) orW_(yyCH)[n] (where, yyCH=SCH1 or SCH2) used at the transmitter, at thedespreaders (224, 226, 225, 227). Then, the signals are integratedduring the symbol period T_(2x) or T_(2y). Since the signals at thereceiver are distorted, PiCH is used to correct the distorted signalphase. Therefore, the signals (x_(R)[n], y_(R)[n]) are multiplied by thecorresponding orthogonal code W_(PiCH)[n], and are integrated during theperiod of T₁ at the integrators (210, 212).

The reverse link PiCH in the cdma2000 system may include additionalinformation such as a control command to control the transmitting powerat the receiver, besides the pilot signals for the phase correction. Inthis case, the additional information is extracted by thede-multiplexer, and the phase is estimated using the part of the pilotsignals having the known phase. The phase corrections are performed atthe second (kind) complex-domain multipliers (242, 246) shown in theleft of FIG. 10 using the estimated phase information through theintegrators (210, 212).

However, the conventional CDMA systems have two problems: The firstproblem is that the strict condition for the linearity of the poweramplifier is required. The second problem is when there are severaltransmitting channels, the signal distortion and the neighboringfrequency interference should be reduced. Therefore, the expensive poweramplifiers with the better linear characteristic are required.

DISCLOSURE OF THE INVENTION

The object of this invention is to provide a method and an apparatus forthe spreading modulation method in CDMA spread spectrum communicationsystems to solve the above mentioned problems. In the spreadingmodulation method according to this invention, the probability for thespread signals (x_(T)[n]+jy_(T)[n]) to make the origin crossingtransition (π-transition) becomes zero not only at n=2t+1, t∈{0, 1, 2, .. . } as in cases of the OCQPSK and POCQPSK spreading modulation butalso at n=2t only except for the time n≡0 (mod min{SF_(PiCH), SF_(DCCH),SF_(SCH2), SF_(SCF1), SF_(FCH)}) when the spreading transmitting datavary. Therefore, the PAR characteristic is improved by using theproposed spreading modulation scheme. In other words, this inventionprovides a method and an apparatus for the spreading modulation methodwith improved PAR characteristic in CDMA spread spectrum communicationsystems.

In accordance with an aspect of this invention an apparatus and a methodfor spreading modulation are invented in CDMA systems with a transmitterand receivers.

The transmitter according to the proposed invention has several channelswith different information. Each channel spreads with the orthogonalcodes using a complex-domain multiplier in addition to the conventionalspreaders, and the spread signals are added. Then the signals arescrambled with the PN sequences, are modulated with a carrier, and aredelivered to an antenna.

The receiver according to the invention demodulates the received signalswith the same carrier used in the transmitter. The demodulated mixedsignals are de-scrambled with the same synchronized PN sequences, andthe de-scrambled signals are de-spread with the same synchronizedorthogonal codes using a complex-domain multiplier in addition to theconventional de-spreaders. Then the desired information is recovered atthe receiver with the conventional signal processing.

In a preferred embodiment, the transmitter according to the inventionhas an additional complex-domain multiplier and a special scramblingcode generator. The probability for the spread signals(x_(T)[n]+jy_(T)[n]) to make the origin crossing transition(π-transition) becomes zero not only for n=2t+1, t∈{0, 1, 2, . . . } butalso for n=2t only except for the time n≡0 (mod min {SF_(PiCH),SF_(DCCH), SF_(SCH2), SF_(SCH1), SF_(FCH})) when the spread transmittingdata vary.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described inconjunction with the drawings in which:

FIG. 1 shows a schematic diagram for a conventional CDMA transmitterwith orthogonal multiple channels;

FIG. 2 shows a schematic diagram for a receiver according to thetransmitter of FIG. 1;

FIG. 3 a shows a schematic diagram for a conventional QPSK spreadingmodulator;

FIG. 3 b shows a schematic diagram for a conventional OQPSK spreadingmodulator;

FIG. 3 c shows a schematic diagram for a conventional CQPSK, OCQPSK,POCQPSK spreading modulator and for a spreading modulator according tothe present invention;

FIG. 3 d shows another schematic diagram for a conventional OCQPSK,POCQPSK spreading modulator;

FIG. 4 a shows a schematic diagram for the scrambling code generator inthe QPSK, OQPSK, CQPSK spreading modulation;

FIG. 4 b shows a schematic diagram for the scrambling code generator inthe OCQPSK spreading modulation;

FIG. 4 c shows another schematic diagram for the scrambling codegenerator in the OCQPSK spreading modulation;

FIG. 4 d shows a schematic diagram for the scrambling code generator inthe POCQPSK spreading modulation;

FIG. 5 a shows schematic diagrams for the first and secondary scramblingcode generators in the cdma2000 modulation;

FIG. 5 b shows a general diagram for the secondary scrambling codegenerator in FIG. 5 a;

FIG. 6 a shows a schematic diagram for a conventional CQPSK, OCQPSK,POCQPSK spreading demodulator and for a spreading demodulator accordingto the present invention;

FIG. 6 b shows a schematic diagram for a conventional OCQPSK, POCQPSKspreading demodulator;

FIG. 7 a shows a signal constellation diagram and transitions;

FIG. 7 b shows four possible transitions of a signal constellationpoint;

FIG. 8 a shows the transition of a signal constellation point for theQPSK spreading modulation;

FIG. 8 b shows the transitions of a signal constellation point for theOQPSK spreading modulation;

FIG. 8 c shows the transitions of a signal constellation point for theCQPSK spreading modulation;

FIG. 9 shows a schematic diagram for a cdma2000 transmitter;

FIG. 10 shows a schematic diagram for a cdma2000 receiver according tothe transmitter of FIG. 9;

FIG. 11 a shows a schematic diagram for a transmitter according to thepresent invention;

FIG. 11 b shows a schematic diagram for the scrambling code generator inthe DCQPSK spreading modulation according to the present invention; and

FIG. 12 shows a schematic diagram for a receiver according to thetransmitter of FIG. 11 a.

<Explanations for main symbols in the drawings>

-   110, 112, 114, 116, 118: gain controller-   120, 122, 124, 126, 128: spreader-   130, 132: adder-   140, 141: spreading modulator-   143, 145: first (kind) complex(-domain) multiplier-   150, 151: scrambling code generator-   160, 162: low-pass filter (LPF)-   170, 172: power amplifier-   180, 182: modulator-   190: adder-   210, 212, 214, 215, 216, 217: integrator-   220, 222, 224, 226, 225, 227: de-spreader-   240, 241: spreading demodulator-   242, 243, 245, 246: second (kind) complex(-domain) multiplier-   260, 262: low-pass filter-   280, 282: demodulator-   510, 520, 530, 550: scrambling code generator-   1220, 1222, 1224, 1226: de-spreader

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be better understood with regard to thefollowing description, appended claims, and accompanying figures. Inthis application, similar reference numbers are used for componentssimilar to the prior art and the modified or added components incomparison with the prior art are described for the present invention indetail.

FIG. 11 and FIG. 12 show schematic diagram for a transmitter and areceiver according to the present invention, respectively. Thetransmitter in FIG. 11 a and the receiver in FIG. 12 are modified fromthe transmitter and the receiver with the POCQPSK spreading modulatorshown in FIG. 9 and FIG. 10. The transmitter according to the inventionhas 5 orthogonal channels: PiCH, DCCH, FCH, SCH1, and SCH2.

Unlike the previous transmitter as in FIG. 9, the transmitter accordingto the invention has an additional complex-domain multiplier (145) shownin the left of FIG. 11 a. The complex-domain multiplier (145) takes thetransmitting data

$\left( {{D_{{SCH}\; 1}\left\lbrack \left\lbrack \frac{n}{{SF}_{{SCH}\; 1}} \right\rbrack \right\rbrack},\mspace{14mu}{D_{{SCH}\; 2}\left\lbrack \left\lbrack \frac{n}{{SF}_{{SCH}\; 2}} \right\rbrack \right\rbrack}} \right)$of SCH1 and SCH2 of statistically high transmitting power as the firstinputs and takes the orthogonal OVSF codes (H_(SCH1)[n], H_(SCH2)[n]) asthe second inputs. And the first orthogonal complex-domain spreadingoccurs at the complex-domain multiplier (145). Other gain-controlledsignals for PiCH, DCCH and FCH spread at the spreaders (1120, 1122,1128) with orthogonal OVSF codes (H_(PiCH)[n], H_(DCCH)[n], H_(FCH)[n]),and are delivered to the adders (130, 132) with the outputs (S_(I)[n],S_(Q)[n]) of the complex-domain multiplier (145). The outputs (x_(T)[n],y_(T)[n]) of the adder (130, 132) are given in EQUATION 31.

$\begin{matrix}\begin{matrix}{{x_{T}\lbrack n\rbrack} = {{G_{p}{H_{\Pi\;{CH}}\lbrack n\rbrack}{D_{\Pi\;{CH}}\left\lbrack \left\lfloor \frac{n}{{SF}_{\Pi\;{CH}}} \right\rfloor \right\rbrack}} +}} \\{{G_{D}{H_{DCCH}\lbrack n\rbrack}{D_{DCCH}\left\lbrack \left\lfloor \frac{n}{{SF}_{DCCH}} \right\rfloor \right\rbrack}} +} \\{{\frac{1}{\sqrt{2}}G_{S\; 1}{H_{{SCH}\; 1}\left\lbrack n \right\}}{D_{{SCH}\; 1}\left\lbrack \left\lfloor \frac{n}{{SF}_{{SCH}\; 1}} \right\rfloor \right\rbrack}} -} \\{\frac{1}{\sqrt{2}}G_{S\; 2}{H_{{SCH}\; 2}\lbrack n\rbrack}{D_{{SCH}\; 2}\left\lbrack \left\lfloor \frac{n}{{SF}_{{SCH}\; 2}} \right\rfloor \right\rbrack}} \\{\simeq {{\frac{1}{\sqrt{2}}G_{S\; 1}{H_{{SCH}\; 1}\lbrack n\rbrack}{D_{{SCH}\; 1}\left\lbrack \left\lfloor \frac{n}{{SF}_{{SCH}\; 1}} \right\rfloor \right\rbrack}} -}} \\{\frac{1}{\sqrt{2}}G_{S\; 2}{H_{{SCH}\; 2}\lbrack n\rbrack}{D_{{SCH}\; 2}\left\lbrack \left\lfloor \frac{2}{{SF}_{{SCH}\; 2}} \right\rfloor \right\rbrack}} \\{{y_{T}\lbrack n\rbrack} = {{G_{F}{H_{FCH}\lbrack n\rbrack}{D_{FCH}\left\lbrack \left\lfloor \frac{n}{{SF}_{FCH}} \right\rfloor \right\rbrack}} +}} \\{{\frac{1}{\sqrt{2}}G_{S\; 2}{H_{{SCH}\; 1}\lbrack n\rbrack}{D_{{SCH}\; 2}\left\lbrack \left\lfloor \frac{n}{{SF}_{{SCH}\; 2}} \right\rfloor \right\rbrack}} +} \\{\frac{1}{\sqrt{2}}G_{S\; 1}{H_{{SCH}\; 2}\lbrack n\rbrack}{D_{{SCH}\; 1}\left\lbrack \left\lfloor \frac{n}{{SF}_{{SCH}\; 1}} \right\rfloor \right\rbrack}} \\{\simeq {{\frac{1}{\sqrt{2}}G_{S\; 2}{H_{{SCH}\; 1}\lbrack n\rbrack}{D_{{SCH}\; 2}\left\lbrack \left\lfloor \frac{n}{{SF}_{{SCH}\; 2}} \right\rfloor \right\rbrack}} +}} \\{\frac{1}{\sqrt{2}}G_{S\; 1}{H_{{SCH}\; 2}\lbrack n\rbrack}{D_{{SCH}\; 1}\left\lbrack \left\lfloor \frac{n}{{SF}_{{SCH}\; 1}} \right\rfloor \right\rbrack}}\end{matrix} & \left\lbrack {{EQUATION}\mspace{14mu} 31} \right\rbrack\end{matrix}$

The spreading modulation takes place at the Spreading Modulator (141)with the first inputs (x_(T)[n], y_(T)[n]) and the second inputs (theprimary scrambling codes; C₁[n] and C₂[n]), and the outputs (I_(T)[n],Q_(T)[n]) are generated. The spreading modulator (141) comprises thescrambling code generator (530) and the complex-domain multiplier (143).The scrambling code generator (530) according to the present inventionshown in FIG. 11 b generates the secondary scrambling codes(C_(scramble, I)[n], C_(scramble, Q)[n]) with the primary scramblingcodes (C₁[n], C₂[n]) as the inputs to improve the PAR characteristic.The complex-domain multiplier (143) takes the x_(T)[n], y_(T)[n] asinputs and the secondary scrambling codes (C_(scramble, I)[n],C_(scramble, Q)[n]) as another inputs. The primary scrambling codes(C₁[n], C₂[n]) in the cdma2000 system are generated by the primaryscrambling code generator (550) using three PN sequences (PN_(I)[n],PN_(Q)[n], PN_(long)[n]) as shown in FIG. 5 a with the followingequation:C ₁ [n]=PN _(I) [n]PN _(long) [n]  [EQUATION 32]C ₂ [n]=PN _(Q) [n]PN _(long) [n−1]The secondary scrambling codes (C_(scramble, I)[n], C_(scramble, Q)[n])shown in FIG. 11 b are given by the following equations.

(1) For n≡0 mod min{SF_(PiCH), SF_(DCCH), SF_(SCH2), SF_(SCH1),SF_(FCH))

$\begin{matrix}{{C_{{scramble}.I}\lbrack n\rbrack} = {C_{1}\lbrack n\rbrack}} & \left\lbrack {{EQUATION}\mspace{14mu} 33} \right\rbrack \\{{C_{{scramble}.Q}\lbrack n\rbrack} = {C_{2}\lbrack n\rbrack}} & \; \\{{\arg\left\{ \frac{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}}{{I_{T}\left\lbrack {n - 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n - 1} \right\rbrack}} \right\}} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}},\pi} \right\}} & \;\end{matrix}$

(2) For n≢0 mod min{SF_(PiCH), SF_(DCCH), SF_(SCH2), SF_(SCH1),SF_(FCH)}C _(scramble,I) [n]+jC _(scramble,Q) [n]=jC ₂ [n]{C _(scramble,I) [n−1]H_(SCH1) [n−1]H _(SCH1) [n]+jC _(scramble,Q) [n−1]H _(SCH2) [n−1]H_(SCH2) [n]}  [EQUATION 34]C _(scramble,I) [n]=−C ₂ [n]C _(scramble,Q) [n−1]H _(SCH2) [n−1]H_(SCH2) [n]C _(scramble,Q) [n]=−C ₂ [n]C _(scramble,I) [n−1]H _(SCH1) [n−1]H_(SCH1) [n]

The spreading modulation according to the present invention is calledthe PCQPSK (Double Complex QPSK) spreading modulation. For|I_(T)[n]|=|Q_(T)[n]|=1 based on the normalization, the possibletransitions of the signal constellation point occurring in the DCQPSKspreading modulation are shown in EQUATION 35 and EQUATION 36. Theprobabilities for {0, +π/2, −π/2, π} transitions are 1/4, 1/4, 1/4, and1/4 for n≡0 mod SF_(min), and 0, 1/2, 1/2, and 0 when n≢0 mod SF_(min)for each transition, respectively. Here, SF_(min)=min{SF_(PiCH),SF_(DCCH), SF_(SCH2), SF_(SCH1), SF_(FCH)}.

(1) For n≡0 mod SF_(min)

$\begin{matrix}{\frac{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}}{{I_{T}\left\lbrack {n - 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n - 1} \right\rbrack}} = {{{\left( \frac{{D_{{SCH}\; 1}\left\lbrack \left\lfloor \frac{n}{{SF}_{\min}} \right\rfloor \right\rbrack} + {{jD}_{{SCH}\; 2}\left\lbrack \left\lfloor \frac{n}{{SF}_{\min}} \right\rfloor \right\rbrack}}{{D_{{SCH}\; 1}\left\lbrack \left\lfloor \frac{n - 1}{{SF}_{\min}} \right\rfloor \right\rbrack} + {{jD}_{{SCH}\; 2}\left\lbrack \left\lfloor \frac{n - 1}{{SF}_{\min}} \right\rfloor \right\rbrack}} \right) \cdot \frac{{H_{{SCH}\; 1}\lbrack n\rbrack} + {{jH}_{{SCH}\; 2}\lbrack n\rbrack}}{\begin{matrix}{{H_{{SCH}\; 1}\left\lbrack {n - 1} \right\rbrack} +} \\{{jH}_{{SCH}\; 2}\left\lbrack {n - 1} \right\rbrack}\end{matrix}}}\frac{{C_{1}\lbrack n\rbrack} + {{jC}_{2}\lbrack n\rbrack}}{\begin{matrix}{{C_{{scramble}.I}\left\lbrack {n - 1} \right\rbrack} +} \\{{jC}_{{scramble}.Q}\left\lbrack {n - 1} \right\}}\end{matrix}}\arg\left\{ \frac{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}}{{I_{T}\left\lbrack {n - 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n - 1} \right\rbrack}} \right\}} \in \left\{ {0,{+ \frac{\pi}{2}},{- \frac{\pi}{2}},\pi} \right\}}} & \left\lbrack {{EQUATION}\mspace{14mu} 35} \right\rbrack\end{matrix}$

(2) For n≢mod SF_(min)

$\begin{matrix}{\left. {{\begin{matrix}{\frac{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}}{{I_{T}\left\lbrack {n - 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n - 1} \right\rbrack}} = {{{jC}_{2}\left\lbrack {n - 1} \right\rbrack}{H_{SCH1}\lbrack n\rbrack}{H_{SCH2}\lbrack n\rbrack}{H_{SCH1}\left\lbrack {n - 1} \right\rbrack}{H_{SCH2}\left\lbrack {n - 1} \right\rbrack}\frac{{NUM}\left\lbrack {n - 1} \right\rbrack}{{DEN}\left\lbrack {n - 1} \right\rbrack}}} \\{= {{{jC}_{2}\left\lbrack {n - 1} \right\rbrack}{H_{a}\lbrack n\rbrack}{H_{a}\left\lbrack {n - 1} \right\rbrack}\frac{{NUM}\left\lbrack {n - 1} \right\rbrack}{{DEN}\left\lbrack {n - 1} \right\rbrack}}} \\{{{NUM}\left\lbrack {n - 1} \right\rbrack} = {\left( {{{C_{I}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} - {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}} \right) +}} \\{{{jH}_{a}\lbrack n\rbrack}\left( {{{C_{I}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} + {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}} \right)} \\{= \left\{ \begin{matrix}\left( {{{C_{I}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} - {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}} \right) \\{{{jH}_{a}\lbrack n\rbrack}\left( {{{C_{I}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} + {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}} \right)}\end{matrix} \right.}\end{matrix}{\begin{matrix}{\left. {{{DEN}\left\lbrack {n - 1} \right\rbrack} = {{{C_{I}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} - {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}}} \right) + {{{jH}_{o}\left\lbrack {n - 1} \right\rbrack}\left( C_{I} \right.}} \\{= \left\{ \begin{matrix}\left( {{{C_{I}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} - {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}} \right) \\{{{jH}_{o}\left\lbrack {n - 1} \right\rbrack}\left( {{{C_{I}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} + {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}} \right)}\end{matrix} \right.}\end{matrix}\left\lbrack {n - 2} \right\rbrack}{H_{SCH1}\left\lbrack {n - 2} \right\rbrack}} + {{C_{Q}\left\lbrack {n - 2} \right\rbrack}{H_{2}\left\lbrack {n - 2} \right\rbrack}}}\; \right)\begin{matrix}{{\arg\left\{ \frac{{I_{T}\lbrack n\rbrack} + {{jQ}_{T}\lbrack n\rbrack}}{{I_{T}\left\lbrack {n - 1} \right\rbrack} + {{jQ}_{T}\left\lbrack {n - 1} \right\rbrack}} \right\}} = {{{C_{2}\left\lbrack {n - 1} \right\rbrack}H_{a}\left\{ n \right\}{H_{a}\left\lbrack {n - 1} \right\rbrack}\frac{\pi}{2}} + {\arg\begin{Bmatrix}{H_{a}\lbrack n\rbrack} \\{H_{a}\left\lbrack {n - 1} \right\rbrack}\end{Bmatrix}}}} \\{= {{\pm \frac{\pi}{2}} + {\arg\left\{ \frac{H_{a}\lbrack n\rbrack}{H_{a}\left\lbrack {n - 1} \right\rbrack} \right\}}}} \\{\in \left\{ {{+ \frac{\pi}{2}},{- \frac{\pi}{2}}} \right\}}\end{matrix}} & \left\lbrack {{EQUATION}\mspace{14mu} 36} \right\rbrack\end{matrix}$Where H_(α)[n]=H_(SCH1)[n]H_(SCH2)[n]. With the bit-wise XOR (eXculisiveOR) operation in EQUATION 6, (α)₂=(SCH1)₂⊕(SCH2)₂).

In the OCQPSK or POCQPSK spreading modulation, as mentioned earlier, theorthogonal Walsh codes with even number subscripts are used except forthe inevitable cases such as the case with the high transmitting datarate for a certain channel of spreading factor (SF) of 2. However, theDCQPSK spreading modulation supports the variable spreading factorkeeping the orthogonal channel property with any orthogonal codes asshown in the previous equations. Thus the orthogonal code is representedby “H” instead of “W” representing the orthogonal Walsh code. Thespreading factor (SF) or size of the orthogonal code need not be thepower of 2.

The outputs (I_(T)[n], Q_(T)[n]) of the Spreading Modulator (141) passthrough the low-pass filters (160, 162) and the amplifiers (170, 172).Then the amplified outputs are delivered to the modulators (180, 182)which modulate the signals into the desired frequency band using acarrier. And the modulated signals are added by the adder (190), anddelivered to an antenna.

FIG. 12 shows a schematic diagram for a receiver according to thetransmitter of FIG. 11 a. The received signals through the antenna aredemodulated at the demodulators (280, 282) with the same carrier used atthe transmitter, and I_(R)[n] and Q_(R)[n] are generated after thesignals pass through the low-pas filters (260, 262). Then, the spreadingdemodulator (241) produces the signals (x_(R)[n], y_(R)[n]) with theprimary scrambling codes (C₁[n], C₂[n]). The spreading demodulator (241)comprises the scrambling code generator (530) and the complex-domainmultiplier (243). The scrambling code generator (520) produces thesecondary scrambling codes (C_(scramble, I)[n], C_(scramble, Q)[n]) withthe primary scrambling codes (C₁[n], C₂[n]) as the inputs to improve thePAR characteristic. The complex-domain multiplier (243) takes I_(R)[n]and Q_(R)[n] as the first inputs and the secondary scrambling codes(C_(scramble, I)[n], C_(scramble, Q)[n]) as the second inputs. The firstand secondary scrambling codes are generated by the same method as inthe transmitter.

In order to pick up the desired channels among the ourputs (x_(R)[n],y_(R)[n]) of the spreading demodulator (241), the signals are multipliedby the same orthogonal code H_(xxCH)[n] (where, xxCH=DCCH or FCH) usedin the transmitter, at the de-spreaders (1224, 1226) or the signal aremultiplied in complex-domain at the complex-domain multiplier (245) inFIG. 12 with the same orthogonal code H_(xxCH)[n] (where, xxCH=SCH1 orSCH2) used in the transmitter. Now, the signals are integrated duringthe symbol period T_(2x) or T_(2y). Since the signals at the receiverare distorted, PiCH is used to correct the distorted signal phase.Accordingly, the signals (x_(R)[n], y_(R)[n]) are multiplied by thecorresponding orthogonal code H_(PiCH)[n], and are integrated during theperiod of T₁ at the integrators (210, 212).

The reverse link PiCH in the cdma2000 system may include additionalinformation such as a control command to control the transmitting powerat the receiver, besides the pilot signals for the phase correction. Inthis case, the additional information is extracted by thede-multiplexer, and the phase is estimated using the part of the pilotsignals having the known phase. The phase corrections are performed atthe complex-domain multipliers (242, 246) using the estimated phaseinformation through the integrators (210, 212).

The DCQPSK spreading modulation according to the present inventionyields the following effects: First, the PAR characteristic is improvedbecause the probability of the origin crossing transition (□-transition)becomes zero only except for the time when the spread transmitting datavary. Second, the flexibility for the channel allocation becomes betterbecause the DCQPSK can use all orthogonal codes while the OCQPSK orPOCQPSK should use the orthogonal Walsh codes with even numbersubscripts.

While the foregoing invention has been described in terms of theembodiments discussed above, numerous variations are also possible.Accordingly, modifications and changes such as those suggested above,but not limited thereto, are considered to be within the scope of thefollowing claims.

1. A transmitting method in CDMA (Code Division Multiple Access) systemswith a transmitting apparatus and receiving apparatus, comprising thesteps of: (a) generating a pilot signal and transmitting data signalsfor several channels with different information, said data signalsincluding a pair of data signals and additional data signals; (b)supplying a pair of the data signals to a complex multiplier andspreading the pair of the data signals with complex orthogonal codes toobtain complex valued first spread signals, and spreading the additionaldata signals with complex orthogonal codes to obtain second spreadsignals; (c) adding the first complex valued spread and the secondsignals; (d) scrambling the added complex valued signals using complexvalued PN (Pseudo-Noise) sequences; (e) modulating the scrambled signalswith a carrier; and (f) transmitting a composite signal created byadding the modulated signals, wherein the complex spreading step and thecomplex scrambling step are arranged to improve the PAR (Peak-to-Averagepower Ratio) characteristic of the transmitter, and wherein the secondcomplex-domain scrambling codes (C_(scramble,I)[n]+jC_(scramble,Q)[n])in the scrambling step are given by the following equations in terms ofthe primary scrambling codes (C₁[n], C₂[n]: (a) when the spreading datavary, C_(scramble,I)[n]+jC_(scramble,Q)[n]=C₁[n]+C₂[n]; and (b) when thespreading data do not vary,C_(scramble,I)[n]+jC_(scramble,Q)[n]=−C₂[n]C_(scramble,Q)[n−1]H_(b)[n−1]H_(b)[n]+jC₂[n]C_(scramble,I)[n−1]H₁[n−1]H_(a)[n].
 2. A transmitting method in CDMA(Code Division Multiple Access) systems with a transmitting apparatusand receiving apparatus, comprising the steps of: (a) generating a pilotsignal and transmitting data signals for several channels with differentinformation, said data signals including a pair of data signals andadditional data signals; (b) supplying a pair of the data signals to acomplex multiplier and spreading the pair of the data signals withcomplex orthogonal codes to obtain complex valued first spread signals,and spreading the additional data signals with complex orthogonal codesto obtain second spread signals; {circle around (c)}) adding the firstcomplex valued spread and the second signals; (d) scrambling the addedcomplex valued signals using complex valued PN (Pseudo-Noise) sequences;(e) modulating the scrambled signals with a carrier; and (f)transmitting a composite signal created by adding the modulated signals,wherein the complex spreading step and the complex scrambling step arearranged to improve the PAR (Peak-to-Average power Ratio) characteristicof the transmitter, and wherein the orthogonal complex-domain spreadingis performed with Hadamard codes and the scrambling codes for thecomplex-domain scrambling are produced using orthogonal Hadamard codes.3. A transmitting method in CDMA (Code Division Multiple Access) systemswith a transmitting apparatus and receiving apparatus, comprising thesteps of: (a) generating a pilot signal and transmitting data signalsfor several channels with different information, said data signalsincluding a pair of data signals and additional data signals; (b)supplying a pair of the data signals to a complex multiplier andspreading the pair of the data signals with complex orthogonal codes toobtain complex valued first spread signals, and spreading the additionaldata signals with complex orthogonal codes to obtain second spreadsignals; {circle around (c)}) adding the first complex valued spread andthe second signals; (d) scrambling the added complex valued signalsusing complex valued PN (Pseudo-Noise) sequences; (e) modulating thescrambled signals with a carrier; and (f) transmitting a compositesignal created by adding the modulated signals, wherein the complexspreading step and the complex scrambling step are arranged to improvethe PAR (Peak-to-Average power Ratio) characteristic of the transmitter,and the orthogonal complex-domain spreading is performed with Walshcodes and the scrambling codes for the complex-domain scrambling areproduced using orthogonal Hadamard codes.
 4. A transmitting method inCDMA (Code Division Multiple Access) systems with a transmittingapparatus and receiving apparatus, comprising the steps of: (a)generating a pilot signal and transmitting data signals for severalchannels with different information, said data signals including a pairof data signals and additional data signals; (b) supplying a pair of thedata signals to a complex multiplier and spreading the pair of the datasignals with complex orthogonal codes to obtain complex valued firstspread signals, and spreading the additional data signals with complexorthogonal codes to obtain second spread signals; {circle around (c)})adding the first complex valued spread and the second signals; (d)scrambling the added complex valued signals using complex valued PN(Pseudo-Noise) sequences; (e) modulating the scrambled signals with acarrier; and (f) transmitting a composite signal created by adding themodulated signals, wherein the complex spreading step and the complexscrambling step are arranged to improve the PAR (Peak-to-Average powerRatio) characteristic of the transmitter, and the orthogonalcomplex-domain spreading is performed with Gold codes and the scramblingcodes for the complex-domain scrambling are produced using orthogonalHadamard codes.
 5. A transmitting apparatus in CDMA (Code DivisionMultiple Access) systems with a transmitting apparatus and receivingapparatus, comprising: (a) means for generating a pilot signal andtransmitting data signals for several channels with differentinformation; (b) means for controlling the signal-gains of the channels(c) means for spreading the gain-controlled signal for each channel; (d)a first complex-domain multiplying means for performing a firstorthogonal complex-domain spreading with the input of the transmittingdata of the supplementary channels and of the OVSF (Orthogonal VariableSpreading Factor) codes; (e) means for adding the output of the firstcomplex-domain multiplying means and the spread signal; (f) a spreadingmodulator, comprising a complex-domain multiplier and a scrambling codegenerator, for modulating the added signal; (g) means for amplifyinglow-pass filtered signal power; (h) means for modulating the amplifiedsignal to the desired frequency band; and (i) means for adding themodulated signal.
 6. A receiving apparatus in CDMA (Code DivisionMultiple Access) systems with a transmitting apparatus and receivingapparatus, comprising: (a) means for demodulating the transmitted signalfrom an antenna using the same carrier used in the transmitter; (b) aspreading de-modulator, comprising a scrambling code generator andcomplex-domain multiplying means, for de-scrambling the modulatedsignal; (c) means for de-spreading the de-scrambled signal to get thedesired channel by integrating for the symbol period proportional to thedata rate of the corresponding channel; and (d) second complex-domainmultiplying means for correcting the phase of the de-spread signal.
 7. Areceiving apparatus as defined in claim 6, wherein the carrier used inthe demodulating means of step (a) in claim 6 include the same wavesused in the transmitter.